1. Field of the Invention
The present invention relates to a dosage unit of the screw-feeder type provided with a device for stirring the product contained in the hopper of the dosage unit.
2. Description of the Prior Art
The field of product dosage systems is well-acquainted with dosage units of the screw-feeder type provided with a hopper, into which the product to be dosed is introduced, and with a helical extractor for the product, which is is driven by a suitable gearmotor located in the lower portion of the hopper.
The hopper is generally shaped as a cone with the apex directed downward and the helical extractor is arranged at the apex.
A drawback of a dosage unit of the above described type is the fact that the product fed into the hopper for subsequent dosage tends to cling to the inclined walls of the hopper and its descent toward the helical extractor is not uniform.
Various embodiments have been proposed in order to obviate the above drawback, but they do not fully solve the problem.
A first embodiment of a conventional unit entails, for example, inducing vibrations in the walls of the hopper, so as to facilitate separation of the product from the walls. However, this embodiment has the drawback that the vibrations can compress the product and this hinders its descent toward the helical extractor.
A second embodiment of a conventional unit uses a hopper with rubber walls or a mixer inside the hopper.
The drawback of this second embodiment is that the mixer can break the product, if the product is fragile, and the rubber walls are subject to contamination.
Furthermore, the above described technical refinements have the additional drawback that they do not allow constant pressure on the helical extractor and therefore do not allow dosage of constant amounts of product.
An aim of the present invention is therefore to provide a dosage unit of the screw-feeder type which has a device for stirring the product fed into the hopper of the dosage unit which allows to maintain constant pressure of the product on the dosage unit.
An object of the present invention is to provide a screw-feeder dosage unit which has a device for stirring the product fed into the hopper of the dosage unit which allows to avoid damage to the product.
A further object of the present invention is to provide a screw-feeder dosage unit in which the stirrer never makes contact with the walls of the hopper of the dosage unit.
A further object of the present invention is to provide a screw-feeder dosage unit with a stirrer which can be removed from the hopper without introducing tools in the hopper.
A further object of the present invention is to provide a screw-feeder dosage unit, with stirrer, which is highly reliable, relatively easy to produce and at competitive costs.